TIDUF75 April   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 System Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  Determining the Number of eFuse Devices to use in Parallel
      2. 2.2.2  Setting up the Primary and Secondary Devices in a Parallel Configuration
      3. 2.2.3  Selecting the CDVDT Capacitor to Control the Output Slew Rate and Start-Up Time
      4. 2.2.4  Selecting the RIREF Resistor to set the Reference Voltage for Overcurrent Protection and Active Current Sharing
      5. 2.2.5  Selecting the RIMON Resistor to set the Overcurrent (Circuit Breaker) and Fast-Trip Thresholds During Steady-State
      6. 2.2.6  Selecting the RILIM Resistor to set the Current Limit and Fast-Trip Thresholds During Start-Up and the Active Sharing Threshold During Steady-State
      7. 2.2.7  Selecting the CITIMER Capacitor to Set the Overcurrent Blanking Timer
      8. 2.2.8  Selecting the Resistors to set the Under-voltage Lockout Threshold
      9. 2.2.9  Selecting the R-C Filter Between VIN and VDD
      10. 2.2.10 Selecting the Pullup Resistors and Power Supplies for SWEN, PG, FLT, and CMPOUT Pins
      11. 2.2.11 TVS Diode Selection at Input and Schottky Diode Selection at Output
      12. 2.2.12 Selecting CIN and COUT
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS25985
      2. 2.3.2 LM94022 and LM94022-Q1
      3. 2.3.3 INA241x
      4. 2.3.4 TLV760
      5. 2.3.5 SN74LVC1G123
      6. 2.3.6 UCC27511A
      7. 2.3.7 CSD18510Q5B
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1.      36
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Bill of Materials
      3. 4.1.3 Altium Project
      4. 4.1.4 Gerber Files
    2. 4.2 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

2.2.4 Selecting the RIREF Resistor to set the Reference Voltage for Overcurrent Protection and Active Current Sharing

In this parallel configuration, the IREF internal current source (IIREF) of the primary eFuse interacts with the external IREF pin resistor (RIREF) to generate the reference voltage (VIREF) for the overcurrent protection and active current sharing blocks. When the voltage at the IMON pin (VIMON) is used as an input to an ADC to monitor the system current or to implement the Platform Power Control (Intel® PSYS) functionality inside the VR controller, VIREF must be set to half of the maximum voltage range of the ISYS_IN input of the controller. This action provides the necessary headroom and dynamic range for the system to accurately monitor the load current up to the fast-trip threshold (2 × IOCP). Equation 8 is used to calculate the value of RIREF.

Equation 8. V I R E F= I I R E F× R I R E F

In the TIDA-050077, VIREF is set at 1V. With IIREF = 25µA (typical), the target RIREF is calculated to be 40kΩ. The closest standard value of RIREF is 40.2kΩ with 0.1% tolerance and a power rating of 100mW. For improved noise immunity, place a 1nF ceramic capacitor from the IREF pin to GND.

Note: Maintain VIREF within the recommended voltage to provide proper operation of the overcurrent detection circuit.